Gelly 1.2 and The Most Cursed Cache Bug

[Gelly](https://github.com/Fingel/gelly) is a music player for Jellyfin and Subsonic servers. I just released version 1.2, which includes support for saving favorites. A favorite is just a boolean flag on an item, nothing more. When the user clicks a cute heart icon or whatever, we flip that boolean, make a HTTP request, and move on. Should be easy to implement right?…